A chain tensioner transmits power of a crankshaft provided in an engine to peripheral auxiliary devices and guides a chain belt that transfers engine oil. The chain tensioner includes a body portion that tensions the chain belt through a pivot, the upper surface of the body portion includes an oil guiding rib that collects the engine oil scattered from the chain belt to the upper part, one surface of the body portion in contact with the upper surface includes a pivot journal, and one surface of the body portion includes a first oil flow path that guides the engine oil to flow down to the pivot journal.